The redox behaviour, optical-absorption spectra and emission properties of U-shaped and elongated disubstituted biisoquinoline ligands and of derived octahedral Fe(II), Ru(II), and Re(I) complexes are reported. The ligands are 8,8′-dichloro-3,3′-biisoquinoline (1), 8,8′-dianisyl-3,3′-biisoquinoline (2), and 8,8′-di(phenylanisyl)-3,3′-biisoquinoline (3), and the complexes are [Fe(2)₃]²⁺, [Fe(3)₃]²⁺, [Ru(1)(phen)₂]²⁺, [Ru(2)₃]²⁺, [Ru(3)₃]²⁺, [Re(2)(py)(CO)₃]⁺, and [Re(3)(py)(CO)₃]⁺. For the ligands, the optical properties as observed in dichloromethane are in line with expectations based on the predominant ¹ππ* nature of the involved excited states, with contributions at lower energies from ¹nπ* and ¹ILCT (intraligand charge transfer) transitions. For all of the Fe(II), Ru(II), and Re(I) complexes, studied in acetonitrile, the transitions associated with the lowest-energy absorption band are of ¹MLCT (metal-to-ligand charge transfer) nature. The emission properties, as observed at room temperature and at 77 K, can be described as follows: (i) the Fe(II) complexes do not emit, either at room temperature or at 77 K; (ii) the room-temperature emission of the Ru(II) complexes (φ_em > 10^–3, τ in the µs range) is of mixed ³MLCT/³LC character (and similarly at 77 K); and (iii) the room-temperature emission of the Re(I) complexes (φ_em ∼3 × 10^–3, τ < 1 ns) is of ³MLCT character and becomes of ³LC (ligand-centered) character (τ in the ms time scale) at 77 K. The interplay of the involved excited states in determining the luminescence output is examined.